LM3886 Mono-block parts

[Bonicon]

Hello,

I have started a gainclone-project now, after building several fullrange-speakers and modding t-amps. However, I regard myself as a beginner in diy electronics, so I am taking things slowly and I try to read up on all things GC.

I will start with a one-channel mono-block, and set out to keep things simple and use this project as a foundation for learning. (Actually, I also bought a kit with an LM380 just to practice soldering and playing around with these chips). Now, "keeping things simple" is always easy to say, but then when I started shopping around for parts I got into the usual state of wanting the exotic (expensive) parts. My question now is therefore, for you who have experience of building GCs, which parts are most important, where should I spend my yen to maximise the performance of my amp?

I have already picked out a 225VAC toroidal transformer (Nuvotem Talema) with 2x18V secondaries (also have the option of 2x25, but my speakers are all 90db+ sensitive so 18*1.4V on the rails should be sufficient, right?). For the PSU caps I am now wondering how much difference premium parts will do, as there is quite difference in price between the 10000uF I am considering. Any thoughts on this is much appreciated.

[pinkmouse]

If it's your first project, go with off the shelf parts. It may well blow up, (my first ever project did). Once you have it up and running, you can swap out parts to your heart's content, and have a baseline to compare upgrades to.

[Nordic]

You will find caps with low ESR and ESL and high temperature tolerance, to be more expensive (keeping your eye on these figures can save you plenty money in looking for alternatives to boutique parts), but worth it.

The large caps and transformer should take a large part of the budget, and the only other part where you will see immediate benifit from average stuff is using a good quality film caps in the main signal path.

Price of resistors does not realy affect sound too much, getting a selection, including some cheap carbon comps, and swapping them out, may tune the sound to your likeing.

I would go with the 25V trannies unless you have 4 ohm speakers, ohms law is a bastard, not to mention that higher voltage = lower crossover distortion.

[Diday]

Hello,

first I would try to get some Panasonic caps from FC series, whose are very great with supa low ESR and much faster then common caps. I have bought some Gain Clone pcbs lately by a new seller here in Germany. Diy-audio-world.com
They have pcbs for different chips! Ich know that they offer for LM 3886, LM 3876 and LM 3875 pcbs. I bought a pcb with panasonic caps which sound great! Powerful and very dynamic.

I have done some hearing tests and resume that more power is not necessary better sound, some caps are to slow and the bass gets slummy.

As far as i know they offer some kits on ebay also for the Hiraga amp.

[Nico Ras]

Originally posted by pinkmouse
If it's your first project, go with off the shelf parts. It may well blow up, (my first ever project did). Once you have it up and running, you can swap out parts to your heart's content, and have a baseline to compare upgrades to.

Hi mouse, I knocked together the GC and I am well, impressed with its performance on first switch on. It still lies around on the bence but that has never bothered me. I will box it when happy only.

On first impressions it is a bit mid band and treble forward and lacks bass guts. I recorder my double bass on the 32 track studer revox and played it through the LM3886 and then throu my normal amps by just spwitching speakers.

On the hole it sounds nice but I assure you that the double bass sounds more like an oversised soundbox on a nylon stringed guitar.

In the mid and highs it is a little tinny, for the loss of a better word, some may call tinny clarity, but I say tinny.

If fingers move over guitar frets there is a specific sound, the GC makes it sound like scraping your thumb nail over a comb, not quite the same. Some may call thi imaging but again I don't know.

Finally a cymbal crash (loud crash) make the amp loose total control and it sound more like braking glass. Cybals are bras not glass.

Overall, if you do not expect the amp to perform miricles and you listen to electronically sysnthesised music with no real life reference, then I agree it sound pretty good. Female voices are a little shrill but very present, but soft male voices dissapears into the background.

Would I finish the amps, yes I think I will. Whill I use them, yes I have decided to use their brightness as the tweeter amp but with a series resistor to tone down the briteness a little, which makes the good HF drivers.

I also had a friend over when playing around. He is not a musician and he seemed to like what he heard very much, so much so that he wants one.

I showed him on the net, these things cost $3300+ but for you, the special price of $ 8 per board and another $30 for a nicely machined box from 10 mm aluminium with two rose wood cheeks for the grand total of $ 40. Now he was impressed.

Ciao

Nico

[pinkmouse]

You could try adding PSU capacitance.

[Bonicon]

Hi,

I bought PCBs from chipamp.com and they got delivered two days ago, however, I have not had a chance to get cracking on this yet due to the current workload. I got an order going from RS here in Japan, and I have been able to find most of the parts I need for my mono-block. Some parts listed in the kit were not available though, so I have chosen some substitutes. First of all, they had the Panasonic FC series, but only up to 2200uF, so I will use the Panasonic TS-HA series 10000uF instead (partnumber ECOS1HA103EA). Also for the amp pcb I got a selection of caps from the Panasonic FC and Nichicon Fine Gold Muse series; I expect to play around with some different caps here to see what impact they have on the sound. I could not find the MUR860 for the rectifier bridge, so I bought the MUR840 which seems to be the closest thing. Any input on this particular choice would be very helpful, I have not heard anything about this diode which according to the datasheet has the same properties apart from the lower voltage rating. I might also try the MUR1620CT as it is available, and it seems to have a faster recovery time than the MUR840. I guess the best approach here is to apply the scientific method and try out different parts for myself and see what results they yield, and then report back here for a more rewarding discussion with the forum members.

As far as the case is concerned, I have been on the lookout for some junk audio (yes, in Japan stuff that does not work, or has scratches, is often sold under the "junk"-conditions, with a "no claim, no return" disclaimer) that I could bastardize and make a case of. However, all the good quality stuff still commends high prices since there are a lot of dudes like me hanging around like vultures in those yahoo-auctions. Your run of the mill electronics is worth almost nothing, but 20-year-old gear that does not work seems to be gold. Too bad it is that stuff I always want... Anyways, I am not sure if I could bring myself to put the dremel into some high-end gear, whether it is junk or not.

So, I think I will have to make my own case, which should provide a lot of opportunities to design things they way I want them to be, and not be constrained by an existing case. I think this will be a long process, but I will try to make some plans and upload some rendering here so that I can get input from you on various design parameters.

[CarlosT]

Originally posted by Diday
Hello,

first I would try to get some Panasonic caps from FC series, whose are very great with supa low ESR and much faster then common caps...

The Panasonic FM series has even better specs and sound pretty nice but unfortunately only go up to 1,000 uF. Still...considering that Peter Daniel runs his GC with 100 uF, 1,000 is more than enough?

[CarlosT]

Originally posted by Nico Ras
...Overall, if you do not expect the amp to perform miricles and you listen to electronically sysnthesised music with no real life reference, then I agree it sound pretty good. Female voices are a little shrill but very present, but soft male voices dissapears into the background...

Wow...that's a bummer, Nico. Are you sure that your caps don't need to break in a little more?

[Bonicon]

Just found these blocks of marble and stone, perhaps not the easiest material to work with but definitely cool. The guy sells them for use as audio and electric outlets enclosures. Have a look at:

http://www.mukai.gr.jp/audio.htm